The phenomenon of debris flow is intermediate between mass movement and solid transport. Flows can be sudden, severe and destructive. Understanding debris flow erosion processes is the key to providing geomorphic expl...The phenomenon of debris flow is intermediate between mass movement and solid transport. Flows can be sudden, severe and destructive. Understanding debris flow erosion processes is the key to providing geomorphic explanations, but progress has been limited because the physical-mechanical properties, movement laws and erosion characteristics are different from those of sediment-laden flow. Using infinite slope theory, this research examines the process and mechanism of downcutting erosion over a moveable bed in a viscous debris flow gully. It focuses specifically on the scour depth and the critical slope for viscous debris flow,and formulas for both calculations are presented.Both scour depth and the critical conditions of downcutting erosion are related to debris flow properties(sand volume concentration and flow depth) and gully properties(longitudinal slope,viscous and internal friction angle of gully materials,and coefficient of kinetic friction). In addition, a series of flume experiments was carried out to characterize the scouring process of debris flows with different properties. The calculated values agreed well with the experimental data. These theoretical formulas are reasonable, and using infinite slope theory to analyze down cutting erosion from viscous debris flow is feasible.展开更多
Beam dams are a highly effective and commonly used open-type check dam in debris-flow hazard mitigation. In this study, dimensional analysis was used to obtain empirical equations for quantitatively determining the se...Beam dams are a highly effective and commonly used open-type check dam in debris-flow hazard mitigation. In this study, dimensional analysis was used to obtain empirical equations for quantitatively determining the sediment-trapping and flow-regulating characteristics of a beam dam. To determine the coefficients of the empirical equations, flume experiments were conducted to simulate the trapping and regulating processes. The flow pattern, trapping, and regulating characteristics were investigated when debris flows passed through a beam dam. Debris-flow bulk density and peak discharge, and sediment-trapping ratios, were measured directly and indirectly. The results showed that three blocking actions occurred, and that blockage-breaking considerably influenced the trapping and regulating performance of the beam dam. The relative opening size and the sediment concentration were the two main factors affecting the performance of the beam dam. The ratio of trapping sediment decreased with relative opening, and increased with sediment concentration as well as reducing ratio of bulk density and reducing ratio of peak discharge. The sediment concentration and relative opening were the leading factors influencing the trapping and regulating sediment of a beam dam, followed by flume gradient. The results showed that the calculated values obtained using empirical equations were in good agreement with the values derived from the experiments, and that the deviation was acceptable. Finally, taking Zechawa Gully as an example, using the empirical equations we designed the opening size of a beam dam aimed to trap sediment and regulate peak discharge of debris flow in the main gully.展开更多
In this paper, the influence of soil liquefaction on the vertical pressure of submarine pipeline was investigated under the wave loading through the wave flume test. The experiment was set with the same waves on the l...In this paper, the influence of soil liquefaction on the vertical pressure of submarine pipeline was investigated under the wave loading through the wave flume test. The experiment was set with the same waves on the liquefied seabed and unliquefled seabed respectively, and the current pipeline vertical pressure was measured with the pressure transducers installed on the two opposite directions （i.e., straight up and straight down） at the same cross-section of the pipeline. The results showed that when the seabed was unliquefied, the two pressure curves varied periodically and overlapped completely, reaching the maximum and minimum at the same time respectively, and the resultant pressure fluctuated within a limited range. However, when the seabed was liquefied, the two pressure curves varied periodically, but they did not overlap completely. They did not reach the maximum （minimum） value at the same time either, and the resultant pressure fluctuated within a wider range. The experiment showed that the submarine stood higher resultant pressure in the vertical direction when the seabed was liquefied, which may cause the frequent sinking and fioatation of the pipeline, leading to its fatigue damage.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.50979103 and 40901007)
文摘The phenomenon of debris flow is intermediate between mass movement and solid transport. Flows can be sudden, severe and destructive. Understanding debris flow erosion processes is the key to providing geomorphic explanations, but progress has been limited because the physical-mechanical properties, movement laws and erosion characteristics are different from those of sediment-laden flow. Using infinite slope theory, this research examines the process and mechanism of downcutting erosion over a moveable bed in a viscous debris flow gully. It focuses specifically on the scour depth and the critical slope for viscous debris flow,and formulas for both calculations are presented.Both scour depth and the critical conditions of downcutting erosion are related to debris flow properties(sand volume concentration and flow depth) and gully properties(longitudinal slope,viscous and internal friction angle of gully materials,and coefficient of kinetic friction). In addition, a series of flume experiments was carried out to characterize the scouring process of debris flows with different properties. The calculated values agreed well with the experimental data. These theoretical formulas are reasonable, and using infinite slope theory to analyze down cutting erosion from viscous debris flow is feasible.
基金supported by the Chinese Academy of Sciences and Organization Department of Sichuan Provincial Party Committee“Light of West China”Program(the key control techniques of glacial debris flow along the Sichuan-Tibet Railway)the National Natural Science Foundation of China(Grant No.41772343)STS Project of the Chinese Academy of Sciences(KFJ-STS-ZDTP015)
文摘Beam dams are a highly effective and commonly used open-type check dam in debris-flow hazard mitigation. In this study, dimensional analysis was used to obtain empirical equations for quantitatively determining the sediment-trapping and flow-regulating characteristics of a beam dam. To determine the coefficients of the empirical equations, flume experiments were conducted to simulate the trapping and regulating processes. The flow pattern, trapping, and regulating characteristics were investigated when debris flows passed through a beam dam. Debris-flow bulk density and peak discharge, and sediment-trapping ratios, were measured directly and indirectly. The results showed that three blocking actions occurred, and that blockage-breaking considerably influenced the trapping and regulating performance of the beam dam. The relative opening size and the sediment concentration were the two main factors affecting the performance of the beam dam. The ratio of trapping sediment decreased with relative opening, and increased with sediment concentration as well as reducing ratio of bulk density and reducing ratio of peak discharge. The sediment concentration and relative opening were the leading factors influencing the trapping and regulating sediment of a beam dam, followed by flume gradient. The results showed that the calculated values obtained using empirical equations were in good agreement with the values derived from the experiments, and that the deviation was acceptable. Finally, taking Zechawa Gully as an example, using the empirical equations we designed the opening size of a beam dam aimed to trap sediment and regulate peak discharge of debris flow in the main gully.
基金supported by the grant from the National Natural Science Foundation of China (No. 41076021)
文摘In this paper, the influence of soil liquefaction on the vertical pressure of submarine pipeline was investigated under the wave loading through the wave flume test. The experiment was set with the same waves on the liquefied seabed and unliquefled seabed respectively, and the current pipeline vertical pressure was measured with the pressure transducers installed on the two opposite directions （i.e., straight up and straight down） at the same cross-section of the pipeline. The results showed that when the seabed was unliquefied, the two pressure curves varied periodically and overlapped completely, reaching the maximum and minimum at the same time respectively, and the resultant pressure fluctuated within a limited range. However, when the seabed was liquefied, the two pressure curves varied periodically, but they did not overlap completely. They did not reach the maximum （minimum） value at the same time either, and the resultant pressure fluctuated within a wider range. The experiment showed that the submarine stood higher resultant pressure in the vertical direction when the seabed was liquefied, which may cause the frequent sinking and fioatation of the pipeline, leading to its fatigue damage.
